Hydrogenated products of thermoplastic norbornene polymers, their production, substrates for optical elements obtained by molding them, optical elements and lenses

ABSTRACT

The present invention provides the hydrogenated product of a thermoplastic norbornene polymer excellent in characteristics as optical materials by reducing the residual amounts of the transition metal atoms originating from the polymerization catalyst used at the polymerization to 1 ppm or less of the hydrogenated product. 
     Reduction of the residual amounts to below the desired level is attained by treating the reaction solution with the adsorbent during or after production of the hydrogenated product from the thermoplastic norbornene polymer. 
     The hydrogenated product of the thermoplastic norbornene polymer thus obtained in which the residual amounts of the transition metal atoms are 1 ppm or less, has a wide utilization field, including a material for optical articles having excellent utilization characteristics such as substrates for optical elements, lenses and the like.

TECHNICAL FIELD

The present invention relates to the hydrogenated product of athermoplastic norbornene polymer excellent in light transmittance,adhesion to metallic films, etc., a method for producing them, asubstrate for optical elements obtained by molding them, an opticalelement and a lens.

BACKGROUND ART

Recently, materials having a high light transmittance are required asoptical materials. Particularly, as to a material for lenses, thosehaving a light transmittance of 90% or more over the whole wavelengthregion of 400 nm to 700 nm when formed into injection-molded articles of3 mm in thickness are considered to be desirable. That is, when thematerial is inferior in transmittance to a part of visible rays, a lensproduced from it takes a color. Further, when the lens is used near to astrong light source, the energy of that part of visible rays of thewavelength is absorbed in the lens, converted to heat in the lens, andas a result the temperature of the lens becomes high. Therefore, thereis a danger of the lens melting even if it is produced with materialswhich are to some degree high in heat resistance.

Hitherto known resins used as optical materials include polymethylmethacrylate (PMMA) and polycarbonate (PC). Among these, PMMA isexcellent in transparency, and when formed into injection-moldedarticles of 3 mm in thickness, its light transmittance reaches 90% and91% at wavelengths of 430 nm and 700 nm, respectively. PMMA, however,has a problem in terms of heat resistance and humidity resistance. Onthe other hand, PC is superior to PMMA in heat resistance and humidityresistance, but when formed into the same injection-molded articles asabove, its light transmittance is at most about 86% at a wavelength of430 nm. Further, when it is molded into lenses, there is a problem ofbirefringence being large.

Recently, the hydrogenated product of a thermoplastic norbornene polymerhas attracted attention as an optical material excellent in heatresistance, humidity resistance and low birefringence. However, thehydrogenated product of a thermoplastic norbornene polymer produced bythe conventional methods was only such that when formed intoinjection-molded articles of 3 mm in thickness, its light transmittanceis less than 90% at a wavelength of 430 nm, although its lighttransmittance is 90% or more at a wavelength of 700 nm. Further, when anoptical element for information recording media is produced byvapor-depositing a metallic film onto a substrate made of thehydrogenated product of a thermoplastic saturated norbornene poller,there is a case where adhesion of the metallic film to the substrate isnot always sufficient as can be seen in the generation of blister owingto the partial peeling-off of the metallic film under high-temperatureand high-humidity conditions. Improvement of such the drawback hastherefore been demanded.

As described later, the present inventors have found that thetransparency and adhesion to metallic film of the hydrogenated productof a thermoplastic norbornene polymer can be improved by reducing thecontent of a transition metal atom present as polymerization catalystresidues in the thermoplastic norbornene polymer. The methods so farused to reduce this content include the following: A method of washingthe polymer solution with a poor solvent; a method of adding a smallamount of the poor solvent to the polymer itself, dissolving thepolymerization catalyst in the poor solvent and separating the catalystsolution; and a method of treating the polymerization solution with anadsorbent (e.g. activated alumina, zeolite, etc.) in the presence of acompound having a hydroxy group (Japanese Patent Application Kokai No.3-66725). If the polymerization catalyst is removed by these methods,however, the content of the transition metal atom present aspolymerization catalyst residues in the polymer treated as above isabout 2 ppm or more. At present, therefore, such the hydrogenatedproduct that the content of the transition metal atom is less than about2 ppm also has not been obtained from this thermoplastic norbornenepolymer.

A method of using a heterogeneous catalyst in the hydrogenation of thethermoplastic norbornene polymer is disclosed in Japanese PatentApplication Kokai No. 1-311120, No. 3-66725, etc. in which carbon,silica, alumina, titania, etc. are used as a carrier. These so far usedcarriers, however, are too short of pore volume and specific surfacearea to give an adsorbing ability to them, so that examples are notknown where a heterogeneous catalyst comprising a catalytic metalsupported on a carrier having a large pore volume and specific surfacearea was used.

DISCLOSURE OF THE INVENTION

The present inventors have extensively studied on the transparency andadhesion to metallic film of the hydrogenated product as a thermoplasticnorbornene polymer. As a result, they have found that the transitionmetal atom originating from the polymerization catalyst remaining intrace amounts in the hydrogenated product exerts an adverse effect onthe transparency and adhesion to metallic film, and also that inproducing the hydrogenated product by hydrogenating the thermoplasticnorbornene polymer in the presence of a solvent and hydrogenationcatalyst, the transition metal atom can easily be removed from thereaction solution by treating the reaction solution witch an adsorbentduring or after hydrogenation of the thermoplastic norbornene polymer,whereby the hydrogenated product having good transparency and adhesionto metallic film can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

According to the present invention, there is provided a method forproducing the hydrogenated product of a thermoplastic norbornene polymerhaving a small content of the transition metal atom originating from thepolymerization catalyst.

(Thermoplastic norbornene polymer)

The term "norbornene" in this specification includes norbornene and itsderivatives.

The thermoplastic norbornene polymer of the present invention containsas impurities polymerization catalyst used in polymerizing thenorbornene monomer. Specific examples of the polymer include thering-opening polymer of the norbornene monomer, addition polymer of thenorbornene monomer, addition polymer of the norbornene monomer with anolefin, and the like.

The norbornene monomer includes for example the following: Norbornene,its alkyl and/or alkylidene derivatives such as 5-methyl-2-norbornene,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene,5-ethylidene-2-norbornene, etc., and these compounds substituted with apolar group (e.g. halogen, etc.); dicyclopentadiene,2,3-dihydrodicyclopentadiene, etc.; dimethanooctahydronaphthalene, itsalkyl and/or alkylidene derivatives and these compounds substituted witha polar group (e.g. halogen, etc.) such as6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7, 8,8a-octahydro-naphthalene,6-ethyl-1,4:5,8-dimethano-1, 4,4a,5,6,7,8,8a-octahydronaphthalene,6-ethylidene-1, 4;5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-chloro-1, 4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-cyano-1,4:5,8-dimethano-1, 4,4a,5,6,7,8,8a-octahydronaphthalene,6-pyridyl-1, 4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-methoxycarbonyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; the adducts ofcyclopentadiene with tetrahydroindene, etc.; the trimer to tetramer ofcyclopentadiene such as4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene,4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene, and the like.

(Polymerization method)

Usually, ring-opening polymerization of the norbornene monomer iscarried out with a catalyst consisting substantially of a transitionmetal compound and an organometal compound of a metal belonging toGroups I to IV of the periodic table. The transition metal compoundincludes the halides, oxyhalides, oxides, etc. of transition metals suchas titanium, molybdenum, tungsten and the like. Specifically, there aregiven TiCl₄, TiBr₄, WBr₄, WCl₆. WOF₄, MoBr₂, MoCl₅, MoOF₄ and the like.The organometal compound of a metal belonging to Groups I to IV includesorganoaluminum compounds, organotin compounds and the like.Specifically, there are given trimethylaluminum, triphenylaluminum,ethylaluminum sesquichloride, tetrabutyltin, diethyltin diiodide,n-butyllithium, diethylzinc, trimethylboron and the like.

Addition polymerization of the norbornene monomer or the norbornenemonomer with an olefin also can be carried out by ring-openingpolymerization with the known transition metal catalysts according tothe known methods. Usually, catalysts composed of a titanium or vanadiumcompound supported on a magnesium compound and an alkylaluminum compoundare used. The titanium or vanadium compound supported on a magnesiumcompound is a composite substance containing at least magnesium,titanium and halogen. A method for producing the composite substance isdisclosed for example in Japanese Patent Application Kokai No. 48-16986,No. 51-29297, No. 52-87489, No. 53-2580 and the like. The vanadiumcompound includes VCl₄, VOBr₂, VO(OCH₃)₂ Cl, VO(OC₃ H₇)₃, VO(OC₄ H₉)Cl₂,etc. and mixtures thereof. The alkylaluminum compound includestrialkylaluminum, dialkylaluminum halide, alkylaluminum dihalide, etc.and mixtures thereof.

The polymerization is stopped after it processed until the desiredmolecular weight is reached. In order to stop the polymerization, thepolymerization catalyst is deactivated, after which it is removed, Fordeactivating the polymerization catalyst, it will suffice to add acatalyst deactivator (e.g. water, alcohol, etc.) to the polymerizationsolution. Thus, the polymerization catalyst precipitates from thepolymerization solution. Since the precipitated polymerization catalystbecomes hard and grows into a large mass by refluxing the reactionsolution, it can be removed more easily. For removing the polymerizationcatalyst, there may be employed and of the methods such as for examplecentrifugation of the deactivated and precipitated polymerizationcatalyst, filtration of the catalyst and washing of the polymerizationsolution after stoppage of the reaction with large amounts of a poorsolvent. Alternatively, the polymerization solution may be treated withan adsorbent (e.g. activated alumina, zeolite, etc.) in the presence ofa compound having a hydroxy group. In removing the catalyst by thesemethods, the transition metal atom originating from the polymerizationcatalyst remains in the polymer in a concentration of about 2 to about10 ppm.

(Hydrogenation)

The thermoplastic norbornene polymer can be converted to itshydrogenated product by saturating the olefin unsaturated groupscontained in the polymer molecule, i.e. a double bond in the main chainand a double bond in the unsaturated ring.

The hydrogenation catalyst usable may be any of those which are commonlyused in the hydrogenation of olefin compounds. For example, there aregiven Willkinson complexes, cobalt acetate/triethylaluminum,acetylacetonatonickel/triisobutylaluminum, etc. and heterogeneouscatalysts in which a catalytic metal (e.g. nickel, palladium, platinum,etc.) has been supported on diatomaceous earth, magnesia, alumina,synthetic zeolite and the like. As described later, a preferredheterogeneous catalyst is those in which the carrier is magnesia,activated alumina or synthetic zeolite, the pore volume is 0.5 cm³ /g ormore, preferably 0.7 cm³ /g or more, and preferably the specific surfacearea is 250 m² /g or more.

The hydrogenation is carried out under a hydrogen pressure of 1 to 150atm. at a temperature of 0° C. to 280° C., preferably 20° C. to 230° C.according to the kind of the hydrogenation catalyst. For example, when acatalyst in which nickel has been supported on activated alumina isused, the temperature is preferably 200° C. to 250° C., more preferably220° C. to 230° C. The percent hydrogenation can be optionallycontrolled by changing hydrogen pressure, reaction temperature, reactiontime, catalyst concentration and the like.

In the present invention, hydrogenation of the thermoplastic norbornenepolymer is usually carried out in an inert organic solvent. Hydrocarbonsolvents are preferred as the organic solvent. Among these, cyclichydrocarbon solvents in which the formed norbornene polymer is highlysoluble are particularly preferred. Specifically, there are givenaromatic hydrocarbons (e.g. benzene, toluene), aliphatic hydrocarbons(e.g. n-pentane, hexane), alicyclic hydrocarbons (e.g. cyclohexane,decalin), halogenated hydrocarbons (e.g. methylene dichloride,dichloroethane) and the like. These solvents may be used in a mixture oftwo or more of them. When the solvent is used, its amount used is 1 to20 parts by weight, preferably 1 to 10 parts by weight based on 1 partby weight of the norbornene polymer.

(Removal of catalyst)

For removing the catalyst after finish of the hydrogenation, it willsuffice to use the usual methods such as centrifugation, filtration andthe like. Methods used for centrifugation and filtration are notcritical, so far as they are carried out under conditions where thecatalyst can be removed. It is preferred, however, that removal of thecatalyst by filtration is simple and efficient. Filtration may becarried out by either of pressure filtration or suction filtration. Useof filtration assistants such as diatomaceous earth, perlite, etc. ispreferred in terms of efficiency. As described later, adsorbentssuitable for the transition metal atom originating from thepolymerization catalyst may be used as the filtration assistant.

When the heterogeneous catalyst, which is the hydrogenation catalyst,contains articles having a particle size of 0.2 μm or more, notsubstantially particles having a particle size of less than 0.2 μm,removal of the heterogeneous catalyst by filtration is so easy that useof such the catalyst is preferred. When the particle size is too small,the particle easily leaks through a filter at the time of filtration,and also removal of the particle becomes difficult even bycentrifugation, as a result of which the amount of the transition metalatom, which is the residue of the polymerization catalyst andhydrogenation catalyst, contained in the hydrogenated product of thethermoplastic norbornene polymer increases. When filtration is carriedout with a filter having a small mesh size in order to prevent the leak,the filter is easily blocked to lower the operation efficiency.

(Adsorption treatment)

In the present invention, the transition metal atom originating from thepolymerization catalyst is removed by treating the reaction solution ofthe polymer with the adsorbent during or after hydrogenation.

Adsorption treatment of the reaction solution is carried out by thefollowing methods.

(1) The adsorbent is added to the reaction solution at the start ofhydrogenation, reaction is carried out and then the hydrogenationcatalyst and adsorbent are removed at the same time.

(2) The adsorbent is added to the reaction solution at the start ofhydrogenation, reaction is carried out and then the adsorbent isremoved, after which the hydrogenation catalyst is removed.

(3) The adsorbent is added to the reaction solution in the course ofhydrogenation, reaction is carried out and then the hydrogenationcatalyst and adsorbent are removed at the same time.

(4) The adsorbent is added to the reaction solution in the course ofhydrogenation, reaction is carried out and then the adsorbent isremoved, after which the hydrogenation catalyst is removed. Adsorptiontreatment after hydrogenation is carried out by the following methods.

(5) The adsorbent is added to the reaction solution after the finish ofhydrogenation, stirring is carried out and then the hydrogenationcatalyst and adsorbent are removed at the same time.

(6) The adsorbent is added to the reaction solution after the finish ofhydrogenation, stirring is carried out and then the adsorbent isremoved, after which the hydrogenation catalyst is removed.

(7) After the finish of hydrogenation, the reaction solution is passedthrough an adsorbent column, after which the hydrogenation catalyst isremoved.

(8) After the finish of hydrogenation, the reaction solution is passedthrough an adsorbent column, in order to remove the hydrogenationcatalyst.

(9) After removal of the hydrogenation catalyst, the reaction solutionis passed through an adsorbent column.

(10) After removal of the hydrogenation catalyst, the adsorbent is addedto the reaction solution, stirring is carried out thoroughly, and thenthe adsorbent is removed.

These methods may be used in combination. The method (8) may bemodified, for example, in such a manner that the hdyrogenation catalystis removed with the adsorbent as a filtration assistant.

Among these methods, the methods (1), (2), (3) and (4) in whichadsorption treatment is carried out during hydrogenation are preferredfrom the standpoint of the efficiency of removal of the transition metalatom originating from the polymerization catalyst, this removal of thetransition metal atom being an object of the present invention. Further,the methods (1) and (2) are preferred in terms of the length oftreatment time and safety of operation. Particularly, the method (1) isvery good in operation efficiency because the hydrogenation catalyst andadsorbent are removed at the same time.

The adsorbent of the present invention is not critical, so far as it cansufficiently adsorb residues resulting from the transition metalcatalyst used in the polymerization and hydrogenation. Preferably,however, the adsorbent is SiO₂ and Al₂ O₃ such as synthetic zeolite,natural zeolite, activated alumina, activated clay, etc. and crystallineor amorphous mixed compositions of these adsorbents. Further, theseadsorbents must have a specific surface area of 50 m² /g or more,preferably 100 m² /g or more, more preferably 200 m² /g or more and apore volume of 0.5 cm³ /g or more, preferably 0.6 cm³ /g or more, morepreferably 0.7 cm³ /g or more. When the specific surface area and porevolume are small, the adsorbing ability is inferior. The particle sizeof the adsorbent is 0.2 μm or more, preferably 10 μm to 3 cm, morepreferably 100 μm to 1 cm. When the particle size is too small, removalof the adsorbent is difficult. While when it is too large, the degree atwhich the column is packed with the adsorbent is small, and also thedegree at which the adsorbent is brought into contact with thetransition metal catalyst residues present in the solution of thehydrogenated product is so small that the adsorbent does not adsorb theresidues sufficiently.

As described above, the adsorption treatment includes:

(I) The reaction solution is passed through a column packed with theadsorbent.

(II) The adsorbent is added to the reaction solution and after stirring,the adsorbent is removed by filtration and the like.

(III) The adsorbent is added to the reaction solution at the time ofhydrogenation.

As described above, the method (III) in which the adsorbent is added tothe reaction solution at the time of hydrogenation is most preferred.

(I) A method of passing the reaction solution through a column packedwith the adsorbent.

The foregoing methods (7), (8) and (9) correspond to this method.

When the packing rate of the column is expressed by ρ(g/m³), thespecific surface area of the adsorbent is expressed by S(m² /g) and theresidence time of the reaction solution is expressed by t(sec), it willsuffice to pass the reaction solution through the column so thatρ(St(sec/m) is 10⁹ or more. Usually, S is about 100 to about 1000 m² /g,and ρ is about 4 to 8×10⁵ g/m³, it will suffice to control the residencetime so as to be 30 sec or more.

In this case, treatment of a large amount of the hydrogenation solutionlowers the adsorbing ability, so that the treatment time needs to beprolonged. Further, it adsorption of the adsorbent reaches saturation,the adsorbent does not adsorb the solution further more. Therefore, at apoint then the concentration of the transition metal atom, thepolymerization catalyst residues, contained in the reaction solutionafter adsorption treatment begins to increase, the column needs to bere-packed with the fresh adsorbent.

(II) A method of adding the adsorbent after hydrogenation.

The foregoing methods (5), (6) and (10) correspond to this method.

When the specific surface area of the adsorbent is expressed by S(m²/g), the amount of the adsorbent added is expressed by m(g), thestirring time of the reaction solution is expressed by t(sec), theamount of the reaction solution to be treated is expressed by V(g), andthe concentration of the hydrogenated product in the reaction solutionis expressed by c, it will suffice to add the adsorbent to the reactionsolution and stir the solution so that Smt/Vc(sec/m) is 10³ or more,preferably 10⁴ or more, more preferably 10⁵ or more, Sm/Vc is 1 or more,preferably 3 or more, particularly preferably 5 or more, and t(sec) is100 or more, preferably 200 or more, more preferably 300 or more. Thestirring time needs to be prolonged depending upon stirring efficiency,but in reality the stirring efficiency is so difficult to control thatit is desirable to prolong the stirring time, so far as the overallefficiency of the operation permits.

Usually, S is about 100 to about 1000 m² /g, and therefore when theconcentration of the hydrogenated product in the reaction solution is10%, it will suffice, for example, to add the adsorbent of 10 g or morebased on 1 Kg of the reaction solution and thoroughly stir the solutionfor 100 seconds or more.

(III) A method Of adding the adsorbent at the time of hydrogenation.

The foregoing methods (1), (2), (3) and (4) correspond to this method.This method is the most preferred embodiment of the present invention.In this case, the adsorbent adsorbs impurities such as gelled resins,etc. at the same time, so that a reduction in the catalytic activityowing to adsorption of impurities by the hydrogenation catalyst is low.Therefore, the hydrogenation can be kept highly active.

The treatment conditions are basically the same as those of the method(II). However, in the cases of the methods (I) and (II) in which theadsorbent is added particularly at the start of hydrogenation, thestirring time in the method (III) becomes long because the hydrogenationtime is the stirring time at the same time. Therefore, it will usuallysuffice to take Sm/Vc alone into account.

In the case of the method (I), it is likewise desirable to use as thehydrogenation catalyst the heterogeneous catalyst in which the catalyticmetal has been supported on the adsorbent of the present invention. Forexample, the heterogeneous catalyst used in the present inventionincludes those in which the catalytic metal (e.g. nickel, palladium,platinum) has been supported on magnesia, activated alumina, syntheticzeolite or the like having a pore volume of 0.5 cm³ /g or more,preferably 0.7 cm³ /g or more, and preferably a specific surface area of250 m² /g or more. Particularly, activated alumina and synthetic zeolitehaving an excellent ability to adsorb impurities are preferred.

For producing the heterogeneous catalyst, it will suffice to follow theknown methods. And also, it will suffice to control the adsorbingability of the carrier according to the conditions of drying andcalcination described in Japanese Patent Application Kokoku No.50-14575, No. 49-32187, No. 49-11312, No. 51-48479 and the like. Forexample, the heterogeneous catalyst in which nickel has been supportedon activated alumina is obtained as follows: An aluminum hydroxidepowder is suspended in a 10 to 20% aqueous nickel sulfate solution sothat its concentration is 10 to 20%; sodium hydroxide is added to thesolution to hydrolyze nickel sulfate, whereby the resulting nickelhydroxide is supported on the surface of aluminum hydroxide; thisaluminum hydroxide powder is recovered by filtration, hardened into amass by extrusion and calcined at 350° C. to 450° C.; the calcined massis brought into contact with hydrogen at 100° C. to 200° C. to reducethe surface, and then heated at 80 ° C. to 120° C. in the presence ofoxygento oxidize the surface of the metal. Thus, an oxide film is formedto obtain a nickel catalyst supported on activated alumina. In thiscase, the surface of nickel is covered with nickel oxide, which ishowever converted to nickel by reduction in the hydrogenation system tofunction as a catalyst.

Since the fine structure of activated alumina changes depending upon theextrusion condition, calcination temperature, pressure and the like, theabove conditions need to be selected so that the pore volume is 0.5 cm³/g or more, preferably 0.7 cm³ /g or more, and preferably the specificsurface area is 250 m² /g or more. When hydrogenation is carried out ata high temperature, it will suffice to select desirable conditions byproperly regulating the oxidation temperature, oxidation time and oxygenconcentration, taking into account that the larger the thickness of theoxide film, the higher the heat resistance of the film. The calcinedproduct thus obtained is pulverized to obtain the heterogeneouscatalyst.

(Hydrogenated product of the thermoplastic norbornene polymer)

The hydrogenated product of the thermoplastic norbornene polymer of thepresent invention, like the conventional ones, is not only excellent inheat resistance, resistance to deterioration by heat and light, humidifyresistance, chemical resistance and the like, but has a small content ofthe transition metal atom originating from the polymerization catalyst.Because of this, the hydrogenated product of thermoplastic norbornenepolymer of the present invention is excellent in transparency ascompared with the conventional ones. And also, for example, opticalelements for information recording medium having a metallic reflectingfilm or metallic recording film produced with the above hydrogenatedproduct of the present invention have a good adhesion to metallic films,as can be seen in that blisters are difficult to appear even inhigh-temperature and high-humidity conditions.

(Additives)

The hydrogenated product of thermoplastic norbornene polymer of thepresent invention can also be used as resin compositions, if necessary,by blending known additives. The additives include for exampleantioxidants, light stabilizers, ultraviolet ray absorbers, lubricants,plasticizers, flame retardants, antistatic agents, heat stabilizers,hydrogenated petroleum resins, dyes, pigments, inorganic and organicfillers and the like.

(Molding)

The hydrogenated product of thermoplastic norbornene polymer of thepresent invention can be molded into a substrate for optical elements bythe usual method. The molding method is not critical, and the usualplastics molding methods such as injection molding, extrusion molding,compression molding the like can be applied.

Optical elements for information recording medium are obtained byforming an information recording film layer on the substrate for opticalelements obtained by molding the hydrogenated product of thermoplasticnorbornene polymer of the present invention. The information recordingfilm layer is usually formed with a metallic film as a metallicreflecting film or metallic recording film. Thus, optical elements forinformation recording medium such as discs for optical recording mediumand cards for optical recording medium can be produced. Formation of themetallic reflecting film is carried out by vapor-depositing a metalhaving a high reflectance such as nickel, aluminum, gold and the like.Formation of the metallic recording film is carried out byvapor-depositing a Tb-Fe-Co alloy, etc. commonly used for the formationof magneto-optical recording films. A method for vapor-depositing ametallic film onto the substrate for optical elements also is notcritical, and the usual vapor deposition methods such as vacuumdeposition, sputtering and the like can be applied.

Plastic lenses can be formed by the known injection molding methodsdescribed, for example, in Japanese Patent Application Kokai No.60-141518, No. 60-225722, No. 61-144316 and the like.

Other optical elements such as Fresnel lens, etc. can be produced byadhering an optical element pattern to the substrate for opticalelements by the known methods.

WORKING EXAMPLE

The present invention will be illustrated specifically with reference tothe following referential examples, examples and comparative examples.

Referential Example 1

Sixty parts by weight of 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene was dissolved in200 parts by weight of cyclohexane, and 1 part by weight of 1-hexene wasadded as a molecular weight-regulating agent. To this solution wereadded 10 parts by weight of a 15% cyclohexane solution oftriethylaluminum as a polymerization catalyst, 5 parts by weight oftriethylamine and 10 parts by weight of a 20% cyclohexane solution oftitanium tetrachloride to start ring-opening polymerization at 30° C.

At a point when the conversion of the monomer to the polymer reached 85%30 minutes after beginning of the polymerization, a 5% cyclohexanesolution of tungsten hexachloride was added. As a result of stirring forfurther 30 minutes, the conversion of the monomer to the polymer reached100%.

To the cyclohexane solution of this polymer were successively added 0.9part by weight of isopropyl alcohol and 7 parts by weight ofion-exchanged water, and the resulting mixture was refluxed at 80° C.for 1 hour. As a result, the polymerization catalyst was hydrolyzed toturn heterogeneous component which separated from the polymer solution.This component was removed by pressure-filtering the solution withdiatomaceous earth (Radiolite #800 produced by Showa Kagaku Co.) as afilter layer to obtain a colorless and transparent solution. Volatilecomponents were removed from a part of this solution to obtain a polymerhaving a number average molecular weight of 25,000 converted to apolystyrene basis by gelpermeation chromatography.

Ten parts by weight of this ring-opening polymer was dissolved in 90parts by weight of cyclohexane, and the concentration of the titaniumatom, which is the residue of the transition metal catalyst, wasmeasured by atomic absorption analysis to find that the concentrationwas 5 ppm based on the ring-opening polymer.

Example 1

A heterogeneous catalyst having a pore volume of 0.8 cm³ /g and aspecific surface area of 300 m² /g in which 0.35 g of nickel and 0.2 gof nickel oxide, each being a weight per 1 g of the catalyst, weresupported on activated alumina used as a carrier, was sieved with a150-mesh sieve, and a fraction having a larger particle size wasselected to obtain the catalyst having a minimum particle size of 0.2 μmor more. The 20% cyclohexane solution of the polymer obtained inReferential Example 1 was put in a pressure-proof reactor, and the abovecatalyst of 2 wt. % based on the polymer was added. Hydrogenation wascarried out at a temperature of 230° C. for 3 hours under a hydrogenpressure of 45/cm². Thereafter, the reaction solution was filteredthrough a 10 double filter layer comprising the upper layer ofdiatomaceous earth (Radiolite #800 produced by Showa Kagaku Co.) and thelower layer of diatomaceous earth (Radiolite #300 produced by ShowaKagaku Co.). The filtrate obtained was successively filtered through acartridge filter having a mesh size of 0.5 and a cartridge filter havinga mesh size of 0.2 μm to remove the catalyst. Thereafter, volatilecomponents in the resulting filtrate were removed with a verticalcylindrical concentrator to obtain the hydrogenated product of thethermoplastic norbornene polymer. This hydrogenated product wasconfirmed to have a percent hydrogenation of nearly 100% by ¹ H-NMR.

Ten parts by weight of this hydrogenated product of the ring-openingpolymer was dissolved in 90 parts by weight of cyclohexane, and theconcentrations of the titanium and nickel atoms were measured by atomicabsorption analysis to find that both of them were below 1 ppm, adetection limit, based on the hydrogenated product.

Example 2

A heterogeneous catalyst having a pore volume of 0.8 cm³ /g and aspecific surface area of 300 m² /g in which 0.35 g of nickel and 0.2 gof nickel oxide, each being a weight per 1 g of the catalyst, weresupported on molecular sieves used as a carrier, was sieved with a50-mesh sieve, and a fraction having a larger particle size was selectedto obtain the catalyst having a minimum particle size of 0.2 μm or more.The 20% cyclohexane solution of the polymer obtained in ReferentialExample 1 was put in an autoclave, and the above catalyst of 2 wt. %based on the polymer was added. Hydrogenation was carried out at atemperature of 230° C. for 3 hours under a hydrogen pressure of 45kg/cm². Thereafter, the reaction solution was filtered through a doublefilter layer comprising the upper layer of diatomaceous earth (Radiolite#800) and the lower layer of diatomaceous earth (Radiolite #300). Thefiltrate obtained was successively filtered through a cartridge filterhaving a mesh size of 0.5 μm and a cartridge filter having a mesh sizeof 0.2 μm to remove the catalyst. Thereafter, volatile components in theresulting filtrate were removed with a vertical cylindrical concentratorto obtain the hydrogenated product of the thermoplastic norbornenepolymer. This hydrogenated product was confirmed to have a percenthydrogenation of nearly 100% by ¹ H-NMR.

Ten parts by weight of this hydrogenated product of the ring-openingpolymer was dissolved in 90 parts by weight of cyclohexane, and theconcentrations of the titanium and nickel atoms were measured by atomicabsorption analysts to find that both of them were below 1 ppm, adetection limit, based on the hydrogenated product.

Comparative Example 1

A nickel catalyst in which nickel has been supported on diatomaceousearth used as a carrier (N-113 produced by Nikki Kagaku Co.; amounts ofnickel and nickel oxide supported, 0.35 g and 0.2 g, respectively, per 1g of the catalyst; pore volume, 0.2 to 0.3 cm³ /g; and specific surfacearea, 100 m² /g) was sieved with a 150-mesh sieve, and a fraction havinga larger particle size was selected to obtain the catalyst having aminimum particle size of 0.2 μm or more.

The 20% cyclohexane solution of the polymer obtained in ReferentialExample 1 was put in a pressure proof reactor, the above nickel catalystof 5 wt. % based on the polymer was added, and then isopropyl alcohol of2 wt. % based on the cyclohexane solution was added for activation ofthe catalyst. Hydrogenation was carried out at a temperature of 190° C.for 3 hours under a hydrogen pressure of 45 kg/cm², and thereafter apart of the reaction solution was sampled and hydrogenated for further 2hours. Each of the 3-hour and 5-hour reaction solutions was filteredthrough a double filter layer comprising the upper layer of diatomaceousearth (Radiolite #800) and the lower layer of diatomaceous earth(Radiolite #300). Thereafter, each filtrate obtained was successivelyfiltered through a cartridge filter having a mesh size of 0.5 μm and acartridge filter having a mesh size of 0.2 μm to remove the catalyst.Thereafter, volatile components in the resulting filtrate were removedwith a vertical cylindrical concentrator to obtain the hydrogenatedproduct of the thermoplastic norbornene polymer. It was confirmed by ¹H-NMR that the percent hydrogenations of the 3-hour and 5-hourhydrogenated products were about 85% and nearly 100%, respectively.

Ten parts by weight of the above hydrogenated product having a percenthydrogenation of nearly 100% was dissolved in 90 parts by weight ofcyclohexane, and atomic absorption analysis was carried out to find thatthe concentrations of the titanium and nickelatoms, which are theresidue of the transition metal catalyst, were 2 ppm and 400 ppm,respectively, based on the hydrogenated product.

Example 3

The hydrogenated product obtained in Example 1 was molded into asubstrate for optical disc having a 1 thickness of 1.2 mm and a diameterof 130 mm with an injection molding machine (DISK Model S-3M produced bySumitomo Heavy Industries, Ltd.) at a mold temperature of 110° C. and aninjection temperature of 300° C. Metallic aluminum was vacuum-depositedon this substrate, and the resulting aluminum-deposited substrate wassubjected to a high-temperature and high-humidity test under conditionsof 70° C.×90% (humidity)×24 hours. As result, abnormalities such asblister, etc. were not observed in adhesion of the metallic aluminumfilm to the substrate.

Comparative Example 2

A substrate for optical disc was prepared in the same manner as inExample 3 except that the hydrogenated product obtained in ComparativeExample 1 was used in place of the hydrogenated product obtained inExample 1. Similarly, metallic aluminum was vacuum-deposited on thissubstrate, and the resulting aluminum-deposited substrate was subjectedto the high-temperature and high-humidity test. As a result, adhesionwas a problem as was observed a blister between the metallic aluminumfilm and substrate.

Example 4

The hydrogenated product obtained in Example 1 was molded into a lensfor projection TV having a thickness of 3 mm with an injection moldingmachine (DISK Model 5-3M produced by Sumitomo Heavy Industries, Ltd.) ata mold temperature of 145° C. and an injection temperature of 290° C.After injection molding, the lens was cooled to 90° C. in 6 minutes. Thelight transmittance of this lens was measured with a spectrophotometerto find that it was 90% or more over the whole wavelength region of 400nm to 700 nm, being 90.4% even at the lowest.

Comparative Example 3

A lens was prepared in the same manner as in Example 4 except that thehydrogenated product obtained in Comparative Example 1 was used in theplace of the hydrogenated product obtained in Example 1. The lighttransmittance of this lens in the region of 400 nm to 450 nm was 88% orless, being 87.9% even at the highest.

Referential Example 2

To a separable flask thoroughly dried and replaced by a nitrogen gas inthe inside were added 27 g of 6-ethylidene-2-tetracyclododecane, and1-hexene and toluene in proportions of 3 mmoles and 120 ml,respectively, based on 27 g of the former.

Further, 3.0 mmoles of triethylaluminum, 0.60 mmole of titaniumtetrachloride and 3.0 mmoles of triethylamine were added, andring-opening polymerization was carried out with stirring at 25° C. for4 hours. After adding 140 g of distilled water, the reaction solutionwas stirred for 1 hour to carry out washing of the solution. Thereafter,a mixed solvent comprising the same amounts of acetone and isopropylalcohol was added to precipitate the ring-opening polymer which was thenfiltered off and dried.

This ring-opening polymer had a molecular weight of 24,000 and a Tg of146° C.

Ten parts by weight of this dried ring-opening polymer was dissolved in90 parts by weight of cyclohexane, and the concentration of the titaniumatom, which is the residue of the transition metal catalyst, in thesolution was measured by atomic absorption analysis to find that theconcentration was 37 ppm based on the ring-opening polymer.

Referential Example 3

Ten grams of the ring-opening polymer obtained in Referential Example 2and 100 ml of cyclohexane were mixed to prepare a solution, and 1 g ofpalladium carbon was added thereto.

The resulting mixture was mixed in a stainless steel ampoule, and air inthe ampoule was replaced by hydrogen to a hydrogen pressure of 50 kg/cm²G. The ampoule was kept at 10° C. for 30 minutes with stirring.Thereafter, the temperature was raised to 120° C. and kept at the sametemperature for 18 hours to finish hydrogenation. After adding 100 g ofdistilled water, the reaction solution was stirred for 1 hour to carryout washing of the solution. Thereafter, a mixed solvent comprising thesame amounts of acetone and isopropyl alcohol was added to precipitatethe hydrogenated product of the ring-opening polymer which was thenfiltered off and dried.

This hydrogenated product had a percent hydrogenation of 99.7% and a Tgof 140° C.

Ten parts by weight of this dried hydrogenated product was dissolved in90 parts by weight of cyclohexane, and the concentrations of thetitanium and palladium atoms, which are the residue of the transitionmetal catalyst, in the solution were measured by atomic absorptionanalysis to find that the concentrations were 9 ppm and 4 ppm,respectively, based on the hydrogenated product.

Example 5

Ten grams of the polymer obtained in Referential Example 2 and 100 ml ofcyclohexane were mixed to prepare a solution, and 1 g of palladiumcarbon and 0.3 g of activated alumina (Neo-bead D powder produced byMizusawa Kagaku Co.; specific surface area, 320 m² /g; pore volume, 0.8cm³ /g; and average particle size, 15 μm) were added thereto. Theresulting mixture was mixed in a stainless steel ampoule, and air in theampoule was replaced by hydrogen to a hydrogen pressure of 50 kg/cm² G.The ampoule was kept at 10° C. for 30 minutes with stirring. Thereafter,the temperature was raised to 120° C. and kept at the same temperaturefor 18 hours to finish hydrogenation. The reaction solution was filteredto remove the palladium carbon and activated alumina, and to thefiltrate was added a mixed solvent comprising the same amounts ofacetone and isopropyl alcohol to precipitate the hydrogenated product ofthe ring-opening polymer which was then filtered off and dried.

This hydrogenated product had a percent hydrogenation of 99.7% and a Tgof 140° C.

Ten parts by weight of this dried hydrogenated product was dissolved in90 parts by weight of cyclohexane, and the concentrations of thetitanium and palladium atoms, which are the residue of the transitionmetal catalyst, in the solution were measured by atomic absorptionanalysis to find that both of them were below 1 ppm of a detection limitbased on the hydrogenated product.

Example 6

Ten parts by weight of the hydrogenated product obtained in ReferentialExample 3 was dissolved in 90 parts by weight of cyclohexane. A columnof 3 cm in radius and 100 cm in height was packed with activated alumina(Neo-based D pellet produced by Mizusawa Kagaku Co.; specific surfacearea, 350 m² /g; pore volume, 0.8 cm³ /g; and particle size, about 3 mm)in a packing rate of 5.0×10⁵ g/m³. Thereafter, the solution obtainedabove was passed through the column so that the residence time was 100seconds. Using the solution flowing out of the column, theconcentrations of the titanium and palladium atoms, which are theresidue of the transition metal catalyst, in the solution were measuredby atomic absorption analysis to find that both of them were below 1 ppmof a detection limit based on the hydrogenated product.

Example 7

Ten parts by weight of the hydrogenated product obtained in ReferentialExample 3 was dissolved in 90 parts by weight of cyclohexane. A columnof 3 cm in radius and 100 cm in height was packed with synthetic zeolite(Mizuka Sieves-13X produced by Mizusawa Kagaku Co.; specific surfacearea, 500 m² /g; pore volume, 1.2 cm³ /g; and particle size, about 1.8mm) in a packing rate of 8.8×10⁵ g/m³. Thereafter, the solution obtainedabove was passed through the column so that the residence time was 100seconds. Using the solution flowing out of the column, theconcentrations of the titanium and palladium atoms, which are theresidue of the transition metal catalyst, in the solution were measuredby atomic absorption analysis to find that both of them were below 1 ppmof a detection limit based on the hydrogenated product.

Example 8

Ten parts by weight of the hydrogenated product obtained in ReferentialExample 3 was dissolved in 90 parts by weight of cyclohexane. Threehundred grams of the resulting solution was put in a 1-liter beaker of10 cm in radius, and 6 g of activated alumina used in Example 1 wasadded thereto. Thereafter, a cylindrical Teflon stirrer chip of 3 cm inlength was put in the beaker and stirred at 100 rpm for 60 minutes bymeans of a magnetic stirrer.

Activated alumina was removed by filtration. Thereafter, using theresulting filtrate, the concentrations of the titanium and palladiumatoms, which are the residue of the transition metal catalyst, in thefiltrate were measured by atomic absorption analysis to find that bothof them were below 1 ppm of a detection limit based on the hydrogenatedproduct.

Example 9

The hydrogenated products obtained in Examples 5 to 8 were each moldedinto a substrate for optical disc having a thickness of 1.2 mm and adiameter of 130 mm with an injection molding machine (DISK Model 5-3Mproduced by Sumitomo Heavy Industries, Ltd.) at a mold temperature of110° C. and an injection temperature of 300° C. Metallic aluminum wasvacuum-deposited on these substrates, and the resultingaluminum-deposited substrates were each subjected to a high-temperatureand high-humidity test under conditions of 70° C.×90% (humidity)×24hours. As a result, abnormalities such as blister, etc. were notobserved in adhesion of the metallic aluminum film to the substrates.

Comparative Example 4

A substrate for optical disc was prepared in the same manner as inExample 9 except that the hydrogenated product obtained in ReferentialExample 3 was used in place of the hydrogenated product obtained inExample 5. Similarly, metallic aluminum was vacuum-deposited on thissubstrate, and the resulting product was subjected to thehigh-temperature and high-humidity test. As a result, adhesion was aproblem as was observed a blister between the metallic aluminum film andsubstrate.

Example 10

The hydrogenated products obtained in Examples 5 to 8 were each moldedinto a lens for projection TV having a thickness of 3 mm with aninjection molding machine (DISK Model 5-3M produced by Sumitomo HeavyIndustries, Ltd.) at a mold temperature of 145° C. and an injectiontemperature of 290° C. After injection molding, the lens was cooled to90° C. in 6 minutes. The light transmittance of these lenses wasmeasured with a spectrophotometer to find that it was 90% or more forany lens over the whole wavelength region of 400 nm to 700 nm, and alsothat it was 90.6%, 90.5%, 90.2% and 90.4%, respectively, even at thelowest. Particularly, the lens produced with the hydrogenated productobtained in Example 1 had the highest light transmittance over the wholewavelength region of 400 nm to 700 nm.

Comparative Example 5

A lens was prepared in the same manner as in Example 10 except that thehydrogenated product obtained in Referential Example 3 was used in placeof the hydrogenated products obtained in Examples 5 to 8. The lighttransmittance of this lens in the region of 400 nm to 450 nm was 90% orless, being 89.0% even at the highest.

<Industrial Applicability>

The resin produced by the method of the present invention, although itsheat resistance, humidity resistance and the like are not different fromthose of the conventional thermoplastic norbornene resins, has animproved transparency, and also its injection-molded product of 3 mm inthickness shows a transmittance of 90% or more to a light of 430 nm inwavelength, so that this resin is suitable as a material for opticalelements requiring transparency. Further, the content of any transitionmetal atom originating from the polymerization catalyst of the resin is1 ppm or less, so that adhesion of the optical element produced withthis resin to metallic film, etc. is good. Therefore, it can be expectedthat this resin is utilized as a material for optical articles having ahigh reliability.

We claim:
 1. The hydrogenated product of a thermoplastic norbornenepolymer of which the content of any transition metal atom originatingfrom the polymerization catalyst is 1 ppm or less.
 2. A substrate foroptical elements obtained by forming the hydrogenated product of athermoplastic norbornene polymer according to claim
 1. 3. An opticalelement for information recording media obtained by depositing aninformation recording film on the substrate for optical elementsaccording to claim
 2. 4. An optical element obtained by depositing anoptical element pattern on the substrate for optical elements accordingto claim
 2. 5. A lens obtained by forming the hydrogenated product of athermoplastic norbornene polymer according to claim
 1. 6. In a methodfor producing a hydrogenated product of a thermoplastic norbornenepolymer by hydrogenating the thermoplastic norbornene polymer insolution in a solvent and in the presence of a hydrogenation catalyst,the improvement which comprises treating the solution with an adsorbenthaving a pore volume of 0.5 cm³ /g or more during or after hydrogenationof the thermoplastic norbornene polymer.
 7. A method according to claim6, wherein the adsorbent is activated alumina or synthetic zeolite.
 8. Amethod according to claim 6, wherein the surface area of the adsorbentis 50 m² /g or more.
 9. A method according to claim 6, wherein the porevolume of the adsorbent is 0.6 cm³ /g or more and the specific surfacearea of the adsorbent is 100 m² /g or more.
 10. A method according toclaim 6, wherein the pore volume of the adsorbent is 0.7 cm³ /g or moreand the specific surface area of the adsorbent is 200 m² /g or more. 11.In a method for producing a hydrogenated product of a thermoplasticnorbornene polymer by hydrogenating the thermoplastic norbornene polymerin solution in a solvent and in the presence of a solvent and ahydrogenation catalyst, the improvement which comprises hydrogenatingthe thermoplastic norbornene polymer with the hydrogenation catalystsupported on a adsorbent having a pore volume of 0.5 cm³ /g or more. 12.A method according to claim 11, wherein the adsorbent is activatedalumina or synthetic zeolite.
 13. A method according to claim 11,wherein the surface area of the adsorbent is 50 m² /g or more.
 14. Amethod according to claim 11, wherein the pore volume of the adsorbentis 0.6 cm³ /g or more and the specific surface area of the adsorbent is100 m² /g or more.
 15. A method according to claim 11, wherein the porevolume of the adsorbent is 0.7 cm³ /g or more and the specific surfacearea of the adsorbent is 200 m² /g or more.